Abstract: A three-dimensional simulation model of the GDI gasoline engine was established, and the spray and combustion models were verified through the constant volume bomb test and the engine bench test. The spray and combustion process adopting single, two-stage and three-stage injection strategies was simulated under 2000r/min full load conditions. The results show that the split injection strategy is beneficial for fuel evaporation; compared with the single injection strategy, the two-stage injection and three-stage injection strategy increase fuel evaporation by 15.6% and 19.5%, respectively. The single injection strategy forms homogeneous mixture at ignition time, while the two-stage injection and three-stage injection strategies form thick stratified mixture near spark plug and thin stratified mixture in other regions at ignition time. Compared with the single injection strategy, the peak value of cylinder pressure of the two-stage injection strategy has been greatly improved. The peak value of cylinder pressure of the three-stage injection strategy is further increased, which is 0.73 MPa higher than that of the single injection strategy. The two-stage injection strategy has a shorter flame development period and a longer combustion period. The three-stage injection strategy has a shorter flame development period and rapid combustion period, which means better combustion characteristics can be gained by employing three-stage injection strategy. Compared with the single injection strategy, both two-stage injection strategy and three-stage injection strategy can improve the indicated thermal efficiency, which increases by 0.4% and 5.9% respectively.

Key words: vehicle engineering, GDI engine, split injection, spray characteristics, combustion characteristics

摘要： 建立GDI汽油机缸内三维仿真模型，通过定容弹试验及发动机台架试验对喷雾、燃烧模型进行验证，模拟分析了2 000 r/min全负荷工况下单次、二次及三次喷油策略下喷雾及燃烧过程。结果表明：多次喷油策略有利于燃油蒸发，与单次喷油策略相比，二次和三次喷油策略燃油蒸发量分别提高15.6%及19.5%；单次喷油策略在点火时刻形成均质混合气，二次及三次喷油策略则在点火时刻形成火花塞附近较浓而其他区域较稀的分层混合气；与单次喷油策略相比，二次喷油策略缸压峰值得到了较大的提升，采用三次喷油策略后缸压峰值进一步增大，比单次喷油策略高0.73 MPa；二次喷油策略具备较短的火焰发展期，快速燃烧期较长，三次喷油策略火焰发展期和快速燃烧期均较短，具备更好的燃烧特性；与单次喷油策略相比，二次喷油策略与三次喷油策略均提高指示热效率，指示热效率分别提高0.4%和5.9%。

关键词: 车辆工程, GDI汽油机, 多次喷射, 喷雾特性, 燃烧特性